Immunohistochemical localization of parathyroid hormone-related protein in developing mouse Meckelʹs cartilage and mandible

In order to clarify the role of parathyroid hormone-related protein (PTHrP) during Meckelʹs cartilage and mandibular development, an immunohistochemical study of PTHrP and its receptor, PTH/PTHrP receptor, was designed to examine their localization in the anterior region of Meckelʹs cartilage including the rostrum, which is known to contribute to the development of the mandible. Meckelʹs cartilage was first observed on day 13 of gestation and PTHrP was faintly localized in the chondrocytes. On day 16 of gestation, at the stage of elongation and initiation of endochondral ossificastitial in Meckelʹs cartilage, PTHrP was localized in the chondrocytes located in the area showing interstitial growth and in and around the nuclei of hypertrophic chondrocytes undergoing endochondral ossification. At day 18 of gestation, endochondral ossification was spread over the entire area proximal to the molar region in Meckelʹs cartilage, except in the mesial fusion site formed by immature chondrocytes. PTHrP was localized in the osteoblasts adjacent to the calcified matrix, but had disappeared from the chondrocytes forming Meckelʹs cartilage. The localization of PTH/PTHrP receptor was similar to that of PTHrP. These results show that localization of PTHrP is spatially and temporally related to the growth of Meckelʹs cartilage.